Like all endocrine glands, parathyroids make a hormone (a small protein capable of causing distant cells in the body to react in a specific manner). Parathyroid hormone (PTH) has a very powerful influence on the cells of the bones which causes them to release their calcium into the bloodstream. Calcium is the main structural component of bones which give them their rigidity--but remember from our first page , the principle purpose of the bones is to provide a storage system for calcium--so our brain will never be without calcium. Under the presence of parathyroid hormone, bones will give up their calcium in an attempt to increase the blood level of calcium. Under normal conditions, this process is very highly tuned and the amount of calcium in our bones remains at a normal high level. Under the presence of too much parathyroid hormone, however, the bones will continue to release their calcium into the blood at a rate which is too high resulting in bones which have too little calcium. This condition is called osteopenia and osteoporosis and is illustrated in this video where the bone develops more "pores" (or holes) and less bone mass. When bones are exposed to high levels of parathyroid hormone for several years they become brittle and much more prone to fractures. Another way in which the parathyroid hormone acts to increase blood levels of calcium is through its influence on the intestines. Under the presence of parathyroid hormone the lining of the intestine becomes more efficient at absorbing calcium normally found in our diet.
The secretion of cortisol is mainly controlled by three inter-communicating regions of the body, the hypothalamus in the brain, the pituitary gland and the adrenal gland . This is called the hypothalamic–pituitary–adrenal axis. When cortisol levels in the blood are low, a group of cells in a region of the brain called the hypothalamus releases corticotrophin-releasing hormone , which causes the pituitary gland to secrete another hormone, adrenocorticotropic hormone , into the bloodstream. High levels of adrenocorticotropic hormone are detected in the adrenal glands and stimulate the secretion of cortisol, causing blood levels of cortisol to rise. As the cortisol levels rise, they start to block the release of corticotrophin-releasing hormone from the hypothalamus and adrenocorticotropic hormone from the pituitary. As a result the adrenocorticotropic hormone levels start to drop, which then leads to a drop in cortisol levels. This is called a negative feedback loop.
If your result is reported as just the word “positive” or “negative,” ask your doctor for a more definite percentage, rating, or other number. Different labs have different cutoff points for calling the cancer either hormone-receptor-positive or hormone-receptor-negative. For example, if less than 10% of your cells stain positive (fewer than 1 in 10), one lab might call this a negative result. Another lab might consider this positive, even though it is a low test result. Research studies have shown that any positive result, no matter how low, suggests that hormonal therapy could help treat the cancer. A score of “0” is needed to completely rule out hormonal therapy as a treatment option.